1. Field of the Invention
The present invention relates to a sheath liquid supplying apparatus, a sheath liquid supplying method and an evaluating method of a sheath liquid supplying condition, and more particularly to an apparatus or method for supplying a sheath liquid to a sheath flow cell by using a syringe in a flow cytometer.
2. Description of the Related Arts
A flow cytometer using a so-called sheath flow method has been well-known as an apparatus for analyzing particles such as a cell, blood cell, or the like in a sample. In this method, a sheath liquid is flown around a sample solution (particle-floating solution) elected from a nozzle in a sheath flow cell to form a sheath flow, whereby the sample solution can be converged into a small flow in the sheath flow cell. The converged sample solution is optically measured for analyzing particles in the sample solution. The xe2x80x9csheath flowxe2x80x9d means a flow for causing particles in the particle-floating solution (sample solution) pass therethrough in a line with precision by converging the sample solution into a small flow having an outside diameter approximately same as that of the particle at the center portion of the sheath liquid that is flowing through an orifice in a laminar flow state. Analysis of various cells has been performed by using a sample solution obtained by adjusting a sample of blood or urine with a dyeing solution, hemolytic agent or reaction reagent.
The sample solution is supplied to the sheath flow cell by a syringe having high quantity accuracy. The sheath liquid is supplied to the sheath flow cell by using a method of applying a predetermined positive pressure (0.2-1.6 kgf/cm2) to the sheath liquid chamber (referring to Japanese Unexamined Publication No. HEI 10(1998)-260129).
However, the supply of the sheath liquid to the sheath flow cell by using a method of applying the positive pressure to the sheath liquid chamber brings a change in viscosity of the sheath liquid in the case of changing the environmental temperature. This change in viscosity brings a change in flow velocity, thereby giving an adverse influence to the optical measurement.
Accordingly, this method requires a sheath liquid temperature adjusting function for maintaining a constant flow velocity of the sheath liquid, as well as requires an air compressor for applying the positive pressure to the sheath liquid chamber or a regulator for adjusting a pressure. This causes a problem that a pressure-adjusting and sheath liquid supplying apparatus is made complicated.
In case where the sheath liquid is supplied to the sheath flow cell by using a syringe that is driven by a stepping motor, the flow velocity is not affected by a change in the environmental temperature. However, the flow velocity of the sheath liquid changes depending upon a mechanical factor such as a pulse of a torque of the stepping motor, whereby a ripple occurs on the sheath liquid and sample solution in the sheath flow cell. Specifically, the sheath flow is brought into an unstable state. As a result, a ground noise of an optical detecting signal is fluctuated, which gives an adverse effect on the optical measurement.
The present invention is accomplished in view of the above circumstances, and aims to provide a sheath liquid supplying apparatus, a sheath liquid supplying method, a flow cytometer including said apparatus, and an evaluating method of a sheath liquid supplying condition wherein a sheath liquid is supplied by using a syringe that is driven by a driving motor. This construction provides that the flow velocity is not affected by an environmental temperature, and prevents a fluctuation in the flow velocity of the sheath liquid due to a mechanical factor such as a pulse of a torque of a stepping motor as well as prevents a fluctuation in a ground noise of an optical detecting signal brought with the fluctuation in the flow velocity.